The objective of this research is to characterize tissue from its intrinsic ultrasonic scattering properties. Measurements of ultrasonic scattering from fresh specimens from autopsy or surgery will be made with a unique apparatus which permits automated scanning of multiple regions. In addition to scattering measurements, attenuation will be measured using a radiation force balance. Scattering will be normalized using attenuation and system parameters to obtain average differential scattering cross section as a function of angle and frequency and also to yield total scattering cross section as a function of frequency. These two intrinsic properties of tissue will provide important descriptions of scatterer sizes and spacings which can be affected by disease. The angle and frequency dependence of average differential scattering cross section will be used to calculate the individual contributions to scattering due to compressibility variations, density variations, and correlation between compressibility and density. The calculations will be carried out over a window of lengths determined by the range of frequencies and angles employed in the measurements to yield intrinsic ultrasonic descriptions of tissue composition which are not available. Acoustic data will be linked to structures in cross sections of corresponding volumes by using a newly developed analysis which permits conversion of scattering from two-dimensional regions to scattering from three-dimensional regions. Normal and abnormal tissues from liver, spleen, breast, and pancreas will be studied. The ability of the various measured and calculated ultrasonic data to characterize tissue will be evaluated using gross specimen descriptions and histologic evaluations of sections as the standard. The results are expected to provide a foundation for a significant increase in diagnostic utility of ultrasound from quantitative intrinsic acoustic parameters of tissue that can be employed to distinguish between normal and diseased tissue and also to determine the severity of disease in circumstances not currently possible.
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